1. Field of the Invention
The present invention relates to mowing equipment and particularly to turf cutting units designed for commercial applications such as golf courses.
2. Discussion of the Relevant Art
During approximately the last 38 years, mowing equipment designed for use by the professional turf industry has become increasingly sophisticated as standards for mower performance have become more demanding. In particular, demand has dramatically increased for a machine that can deliver the highest quality of cut on a golf course fairway which is likely to have a variety of contours. Another aspect of the industry, especially in North America, is the growth of "daily fee" golf courses, which are open to the public for a fee. As compared to the more traditional private golf clubs, daily fee courses tend to be more sensitive to competitive market forces, which demand greater cost consciousness. As a result, the demand for more cost effective mowing equipment capable of performing the highest quality cut has increased substantially as the industry has continued to evolve. The flex-head cutting unit addresses these requirements by providing a mowing machine that is more efficient than the current industry standard, employing wider cutting units which are capable of operating at higher ground speeds, without loss of quality of cut.
Due to the very large area of turf involved with commercial golf courses, turf cutting units have been developed which cut a wide path for greater efficiency. Typically, such units are either incorporated into a motorized wheeled vehicle, or can be towed behind such a vehicle. A familiar design is the reel type grass cutting mechanism which is essentially a rotating cylinder fitted with blades which cut against a static bed-knife. See, e.g., U.S. Pat. No. 5,343,680 to Reichen et al. and U.S. Pat. No. 5,497,603 to Short.
One difficulty which has long existed as concerns mowing equipment is the difficulty in achieving a balance between a cutting unit which cuts an exceptionally wide path, while also providing an exceptionally smooth and even cut. In particular, difficulty has been encountered in connection with the numerous contours and hills which typically are designed into golf courses. Typically, when such contours are encountered, conventional reel-type cutting units will have a tendency to follow ground contours unevenly, resulting in a cut which has an irregular appearance. The current industry standard for achieving the highest quality of cut on fairways is a 22" wide cutting unit which is able to deliver the requisite quality of cut, but sacrifices speed and efficiency (as opposed to wider cutting units). Another problem associated with such prior art systems relates to the speed at which they may be towed across the ground. For example, current state of the art light-weight fairway cutting units equipped with a 22" cutting heads have a maximum ground speed of about 6 miles per hour. This limits the rate at which the cutting process occurs and results in greater labor costs.
Various prior art turf cutting units have been developed to help eliminate the foregoing problems, but none have been completely satisfactory. Existing reel-type grass cutting units commonly incorporate two ground contacting rollers. The rollers generally support a frame unit which itself supports a rotating cutting cylinder. In typical systems incorporating a pair of rollers, the rollers are positioned at the front and rear of the cutting unit and are rigidly mounted to the frame. The mounting mechanism is typically designed to allow the rollers to be manually adjusted so that the height of the frame (and therefore the cutting height) may be adjusted relative to the ground.
In conventional two roller-type reel cutting units, the surfaces of the rollers which contact the ground define a plane. Where the terrain closely matches this plane, the height of cut will be constant across the width of the machine. Machines having multiple cutting units, such as is shown in U.S. Pat. No. 5,497,603, are capable of producing a uniform height of cut if the terrain closely matches the planes of its individual cutting units. However, where the terrain does not match the plane of the rollers, the height of cut will be inconsistent across the width of the cutting unit because at least a portion of one of the rollers will not be in contact with the ground. In addition, minor variations in the balance of the cutting unit (as well as the interaction between the machine and cutting unit through a suspension mechanism) make it difficult to predict which side of the cutting unit will not be in full contact with the ground. Thus, in machines with multiple cutting units, the height of cut of a particular cutting unit may not match the height of cut of its adjacent cutting units. As a result, the turf may display this discrepancy in the form of variations in heights of cut among the various cutting units, resulting in the appearance of lines in the turf that are often considered objectionable. Current state of the art designs minimize this problem by employing relatively narrow (22") cutting units.
A further problem with conventional reel-type grass cutting mechanisms relates to the conditions of the turf and the cutter mechanism weight distribution as between the front and rear rollers. Where turf conditions present a firm, unyielding surface to the cutting unit, variations in the weight distribution between the front and rear rollers will not produce any variation in height of cut, so long as there is sufficient weight on each roller to keep it solidly on the ground. However, where the surface is more elastic and spongy, cutter designs of the prior art may interact with the turf to produce variable height of cut. In particular, the added weight on one roller can cause it to penetrate the turf excessively, producing a variable height of cut.
The foregoing problem is often compounded by the positioning of the propulsion arm attachment point above the plane defined by the two rollers. In such cases, motive force provided by the propulsion arm and the resultant drag of the rollers will create torque which will tend to cause the cutting unit to rotate about its lateral axis. Where the turf is particularly heavy, the torque may be sufficient to cause the rear roller of the mower to lift off the ground, thereby producing a variation in the cutting height. This phenomenon is acknowledged in U.S. Pat. No. 5,343,680 (see column 1, lines 22-29). In that patent, it is also acknowledged that the invention described therein is an incomplete solution of this problem (see col. 6, lines 37-41). Other examples showing that designers have recognized this problem are the Toro 5100, Toro 5300, Jacobsen LF-100, and Jacobsen LF-128, where spring mechanisms linking the propulsion arm and the cutting unit cause weight to be transferred from the front roller to the rear roller. The flex-head design according to the present invention improves weight distribution between the front and rear rollers as a function of draft, thereby permitting higher ground speeds to be achieved, along with increased productivity.